Predictive Value of Preoperative Neutrophil-to-Lymphocyte Ratio (NLR) and Soluble Urokinase-Type Plasminogen Activator Receptor (suPAR) for Biochemical Recurrence After Radical Prostatectomy

Introduction

Prostate cancer (PCa) is one of the common malignant tumors in the male genitourinary system, and its incidence has shown an upward trend worldwide [1,2]. Radical prostatectomy is the primary treatment for localized PCa; however, some patients experience biochemical recurrence (BCR) after surgery, which seriously impairs their quality of life and prognosis [3,4]. BCR is defined as 2 consecutive detections of serum prostate-specific antigen (PSA) levels of 0.2 ng/mL or higher following radical treatment for PCa [5]. Currently, identifying effective biomarkers to predict BCR after radical prostatectomy is of great significance for guiding clinical treatment and improving patient prognosis. While established predictors such as PSA kinetics, Gleason score, and surgical margin status are routinely used, there remains an unmet need for biomarkers reflecting systemic inflammatory and tumor invasion processes.

The neutrophil-to-lymphocyte ratio (NLR) is an inflammatory-immune indicator derived from routine blood tests, which can reflect the balance between inflammation and immunity in the human body [6]. Existing studies have confirmed that the NLR is associated with the prognosis of various malignant tumors [7,8]. It has been reported that the NLR can predict the prognosis of patients with locally advanced or castration-resistant PCa, and patients with higher NLR levels are more likely to have a poorer prognosis [9]. Specifically, the NLR serves as an effective prognostic biomarker in PCa, as it is closely correlated with the survival time, PSA levels, and treatment response, as evaluated by the Response Evaluation Criteria in Solid Tumors (RECIST), of patients receiving second-line chemotherapy [10].

The soluble urokinase-type plasminogen activator receptor (suPAR) is the soluble form of the urokinase plasminogen activator receptor (uPAR). The suPAR is involved in processes such as extracellular matrix degradation, cell migration, invasion, and angiogenesis, and its expression is elevated in a variety of inflammatory diseases and malignant tumors [11,12]. Studies have shown that suPAR levels are increased in tumor tissues of various cancers, and an elevated suPAR is associated with poor prognosis [12–14]. Specifically, research has shown that the suPAR significantly inhibits cell growth, promotes cell apoptosis, and reduces the migratory ability of PCa cells and their invasiveness into a Matrigel matrix [15]. In the field of PCa, existing studies have suggested that serum suPAR levels can serve as a potential diagnostic biomarker for early detection of PCa and prediction of patient prognosis [16]. However, its value in predicting BCR after radical prostatectomy, especially when used in combination with the NLR, has been rarely investigated.

The NLR and suPAR have complementary mechanisms of action: the NLR reflects the imbalance between inflammatory and immune responses, primarily representing the immunologic pathway, while the suPAR is involved in tumor invasion and metastasis via extracellular proteolytic activity. Theoretically, their combined use for prediction can exert a synergistic effect and improve predictive efficacy. We hypothesize that the preoperative NLR combined with suPAR improves prediction of BCR after radical prostatectomy compared with either marker alone. However, there is a paucity of studies on the predictive value of preoperative NLR combined with suPAR for BCR after radical prostatectomy for PCa. This study aimed to detect preoperative NLR and suPAR levels, explore the feasibility of their combined use in predicting postoperative BCR, and provide new predictive indicators and insights for clinical practice.

Material and Methods

STUDY PARTICIPANTS:

This was a single-center retrospective cohort study. We retrospectively analyzed 366 patients who underwent laparoscopic radical prostatectomy for PCa at our hospital between January 2020 and April 2023. After strict application of inclusion and exclusion criteria, a total of 245 patients with PCa were included in the study. Inclusion criteria were as follows: (1) pathologically confirmed diagnosis of PCa; (2) newly diagnosed and without any prior anti-tumor treatment (such as chemotherapy, radiotherapy, or endocrine therapy) before admission; (3) all patients underwent laparoscopic radical prostatectomy; (4) complete clinicopathological data and postoperative follow-up records; and (5) age 18 years or older. Exclusion criteria were as follows: (1) presence of other malignant tumors; (2) severe infections, autoimmune diseases, or other conditions affecting inflammatory markers; (3) prior anti-tumor treatment before admission; and (4) missing clinical data or in-hospital death during the treatment period. According to whether BCR occurred after surgery, the patients with PCa were divided into non-BCR (n=183) and BCR (n=62) groups. This study was approved by the ethics committee of our hospital and complies with the Declaration of Helsinki.

MEDICAL RECORD DATA COLLECTION:

General clinical data and tumor-related information for all study participants were collected through the hospital’s electronic medical record system. Specific variables included age, body mass index (BMI), preoperative serum PSA level, Gleason score, total prostate volume, T stage, seminal vesicle invasion, and surgical margin status. Preoperative PSA levels were measured using a standardized chemiluminescent immunoassay in the hospital’s central laboratory. All pathological parameters, namely Gleason score, T stage, seminal vesicle invasion, and surgical margin status, were evaluated by 2 experienced uropathologists blinded to patient outcomes. Peripheral venous blood was collected from each patient before surgery for routine blood tests using an automated hematology analyzer. The NLR was calculated as NLR=neutrophil count/lymphocyte count. Additionally, 5 mL of fasting venous blood was collected from each patient upon admission in the morning and drawn into collection tubes. The blood samples were allowed to clot naturally at room temperature for 30 minutes. After coagulation, the samples were centrifuged at 2000 rpm for 20 minutes, and the supernatant serum was collected and stored at −80°C for subsequent use.

Serum suPAR levels were measured using enzyme-linked immunosorbent assay (ELISA) kit. All samples were tested in duplicate, and the mean concentration was calculated for the final analysis. The Human suPAR ELISA kit (JLC23303; Jiangxi Jianglan Pure Biological Reagent Co, Ltd, China) was used, with a detection range of 0.25 to 8 ng/mL. The intra- and inter-assay coefficients of variation were less than 10% and less than 15%, respectively.

FOLLOW-UP AND OUTCOME ASSESSMENT:

After discharge, the patients were followed up for 2 years via outpatient re-examinations: once every 3 months in the first year and once every 6 months in the second year. The follow-up ended in April 2025 or upon the occurrence of BCR. The diagnostic criteria for BCR were the absence of metastatic or recurrent lesions detected by imaging during follow-up and 2 consecutive serum PSA levels greater than 0.2 ng/mL.

STATISTICAL ANALYSIS:

Data were statistically analyzed and graphed using GraphPad Prism 9.5.0 software (GraphPad Software Inc, San Diego, CA, USA) and SPSS 21.0 (IBM Corp, Armonk, NY, USA). The Shapiro-Wilk test was used to assess normality. Normally distributed continuous variables are presented as mean±standard deviation (SD) and were compared between groups using the independent samples t test. Non-normally distributed continuous variables are expressed as median (interquartile range) and were analyzed using the Mann-Whitney U test. Categorical variables are presented as number (percentage) and were compared using the chi-square test. The Cox proportional hazards regression model was used to analyze the influencing factors of postoperative BCR in patients with PCa. The proportional hazards assumption was verified using Schoenfeld residuals. The receiver operating characteristic (ROC) curve was used to evaluate the predictive value of serum NLR and suPAR levels alone and in combination for postoperative BCR in patients with PCa. The combined NLR-suPAR predictor was derived from a logistic regression model incorporating both markers, and the predicted probabilities from this model were used for subsequent ROC and survival analyses. The Kaplan-Meier method was used to draw the postoperative BCR curves of the patients, and the log-rank test was used to compare the differences in recurrence risk among different groups. Missing data were handled using complete-case analysis, and only patients with complete data for all variables were included in the final analysis. All P values were derived from 2-sided tests. A P value <0.05 was considered statistically significant.

Results

CLINICAL BASELINE CHARACTERISTICS OF THE STUDY POPULATION:

A total of 245 patients who underwent laparoscopic radical prostatectomy were included in this study. After a 2-year postoperative follow-up, BCR occurred in 62 patients (25.31%), while 183 patients (74.69%) remained free of BCR (non-BCR group). There were no statistically significant differences between the 2 groups in terms of age (t=1.106, P=0.270), BMI (t=0.817, P=0.415), or total prostate volume (t=1.363, P=0.174; Table 1). However, significant differences were observed in tumor-related characteristics. The BCR group had significantly higher proportions of patients with a preoperative serum PSA of 20 ng/mL or higher (70.97% vs 51.91%), Gleason score of 8 or higher (59.68% vs 39.89%), pathologic T3–T4 stage (56.45% vs 36.61%), positive seminal vesicle invasion (43.55% vs 25.68%), and positive surgical margins (27.42% vs 10.38%) compared with the non-BCR group. These differences were all statistically significant (χ2=6.850, 7.329, 7.501, 7.011, and 10.721, respectively; all P<0.05; Table 1).

COMPARISON OF PREOPERATIVE NLR AND SUPAR LEVELS BETWEEN THE 2 GROUPS:

We compared preoperative NLR and serum suPAR levels between the 2 groups. The results showed that patients in the BCR group had significantly higher preoperative NLR (2.10 [1.90–2.50] vs 3.00 [2.58–3.73]) and suPAR levels (3.25±0.65 ng/mL vs 2.15±0.63 ng/mL) than did patients in the non-BCR group. These differences were statistically significant (Z=−8.784, P<0.001; t=11.760, P<0.001, respectively; Figure 1). These results indicate that the serum levels of NLR and suPAR in PCa patients with recurrence are significantly higher than those in patients without recurrence.

UNIVARIATE AND MULTIVARIATE COX REGRESSION ANALYSIS OF FACTORS ASSOCIATED WITH POSTOPERATIVE BCR IN PCA:

Using follow-up time as the time variable and postoperative BCR (no BCR=0; BCR=1) as the outcome, univariate Cox regression analyses were performed. Variables included age, BMI, preoperative PSA, Gleason score, pathologic T stage, seminal vesicle invasion, positive surgical margins, preoperative NLR, and suPAR levels, which were selected based on the baseline characteristics in Table 1. Univariate analysis revealed that preoperative PSA, Gleason score, pathologic T stage, seminal vesicle invasion, positive surgical margins, preoperative NLR, and suPAR levels were all significantly associated with postoperative BCR (all P<0.05; Table 2).

Subsequently, variables that showed statistical significance in the univariate analysis were entered into a multivariate Cox proportional hazards regression model. The multivariate analysis demonstrated that preoperative PSA of 20 ng/mL or higher (HR=1.886, 95% CI=1.047–3.396, P=0.034), pathologic T3–T4 stage (HR=1.762, 95% CI=1.044–2.974, P=0.034), positive surgical margins (HR=1.943, 95% CI=1.084–3.482, P=0.026), high NLR expression (HR=1.348, 95% CI=1.040–1.747, P=0.024), and high serum suPAR expression (HR=3.451, 95% CI=2.186–5.448, P<0.001) were independent risk factors for BCR after radical prostatectomy in patients with PCa (Table 2).

PREDICTIVE VALUE OF NLR, SUPAR, AND THEIR COMBINATION FOR POSTOPERATIVE BCR IN PCA:

Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive value of NLR, suPAR, and their combination for postoperative BCR in patients with PCa. The optimal cut-off values were determined using the Youden index (J=sensitivity + specificity − 1). The results showed that the area under the ROC curve (AUC) of NLR for predicting postoperative BCR was 0.873 (95% CI: 0.826–0.919), with a cut-off value of 2.350, sensitivity of 90.32%, and specificity of 67.21%; the AUC of suPAR for predicting postoperative BCR was 0.881 (95% CI: 0.829–0.934), with a cut-off value of 2.750, sensitivity of 83.87%, and specificity of 80.33%; while when NLR and suPAR were combined, the AUC for predicting postoperative BCR significantly increased to 0.943 (95% CI=0.911–0.975), with a cut-off value of 0.350, sensitivity of 85.48%, and specificity of 92.35% (Figure 2). Further comparison and analysis of AUC through MedCalc software showed that there was no statistically significant difference in the AUC between NLR and suPAR for standalone prediction (P=0.802). However, the AUC of the combination of NLR and suPAR for predicting postoperative BCR in patients with PCa was significantly better than that of NLR and suPAR alone (all P<0.05; Table 3).

POSTOPERATIVE BCR RATES STRATIFIED BY NLR, SUPAR, AND THEIR COMBINED EXPRESSION LEVELS:

To further explore the relationship between NLR, suPAR levels, and postoperative BCR in PCa, the cut-off values derived from the ROC curves of NLR (2.350), suPAR (2.750), and their combination (0.350) were used as thresholds to classify patients with PCa into high-expression groups and low-expression groups. The postoperative BCR rates were then compared among the groups. The results showed that the postoperative BCR rates in the high-expression groups of NLR, suPAR, and their combination were 48.28%, 59.09%, and 79.10%, respectively. These rates were significantly higher than those in the corresponding low-expression groups: 4.65% (low NLR), 6.37% (low suPAR), and 5.06% (low combined expression). Statistically significant differences in postoperative BCR rates were observed among the 3 pairs of groups (all P<0.001; Table 4).

HIGH LEVELS OF NLR AND SUPAR INCREASE RISK OF POSTOPERATIVE BCR IN PATIENTS WITH PCA:

Subsequently, the Kaplan-Meier curve for postoperative BCR of patients with PCa was plotted based on the distribution comparison of the Kaplan-Meier curve and log-rank test. The results showed that the Kaplan-Meier curves of patients with high expression of NLR, suPAR, or their combination were shifted to the left compared with those of patients with low expression of NLR, suPAR, or their combination. This leftward shift indicates a significantly higher risk of postoperative BCR in the high-expression groups (all P<0.001; Figure 3). These findings confirm that high preoperative levels of NLR and suPAR were associated with an increased risk of postoperative BCR in patients with PCa.

Discussion

CLINICAL IMPLICATIONS:

The clinical translational value of this study’s results is mainly reflected in the concept of risk stratification-guided individualized management, which can optimize PCa clinical practice from 3 dimensions: preoperative assessment, postoperative precision surveillance, and therapeutic intervention. In terms of preoperative assessment, NLR and suPAR can serve as noninvasive prognostic indicators to complement existing staging systems (eg, TNM staging, Gleason score) for improved risk stratification. For example, if patients at intermediate risk with preoperative Gleason score of 7 and T2 stage simultaneously have an NLR greater than 2.350 and suPAR greater than 2.750, their postoperative BCR risk is as high as 79.10%, and they can be reclassified as high-risk. In this case, clinicians may consider adding neoadjuvant therapy, such as androgen deprivation therapy or chemotherapy, preoperatively to reduce tumor burden and lower recurrence risk. In contrast, for intermediate-risk patients with combined low expression of NLR and suPAR, the BCR rate is only 5.06%; therefore, radical prostatectomy alone can be prioritized, to avoid overtreatment. Regarding postoperative precision surveillance, the “one-size-fits-all” follow-up model (once every 3 months in the first year, once every 6 months in the second year) can be optimized. For patients with combined high expression, PSA re-examinations should be conducted every 2 months in the first 6 postoperative months, every 3 months from 6 to 12 months, and every 4 months after 1 year; for patients with combined low expression, the interval can be extended to once every 4 months in the first year and once every 6 months after 1 year, balancing early recurrence detection and resource conservation. In the aspect of therapeutic intervention, NLR and suPAR are not only predictive biomarkers but also potential therapeutic targets. For patients with a high NLR, anti-inflammatory drugs, such as non-steroidal anti-inflammatory drugs, can be used to regulate the inflammatory microenvironment; existing studies have confirmed that aspirin can reduce the recurrence risk of patients with PCa [23]. For patients with high suPAR, uPAR-targeted inhibitors, such as anti-uPAR monoclonal antibodies and uPAR antagonists, have entered clinical trials for various solid tumors and may become a new option for PCa adjuvant therapy in the future [24]. Additionally, combined detection can be used to evaluate treatment efficacy: if the postoperative levels of NLR and suPAR in patients continuously decrease, it indicates effective treatment and reduced recurrence risk; if the levels increase instead of decrease, vigilance should be raised for active residual tumor cells, and the treatment regimen should be adjusted promptly.

LIMITATIONS:

Despite the valuable findings of this study, it still has the following limitations that need to be addressed in subsequent research. First, the study adopted a single-center retrospective design with patients from a single Asian (Chinese) center. Ethnic or regional differences can exist in PCa pathological features (eg, Gleason score distribution), baseline inflammatory levels, and suPAR expression patterns, which can affect the generalizability of the combined model. Additionally, although we adjusted for known confounders, potential residual confounding from unmeasured factors, such as unmeasured inflammation sources, medication use, and comorbidities, cannot be ruled out. Multi-center, multi-ethnic prospective studies are needed to validate the results. Future research should also explore incorporating NLR and suPAR into established prognostic nomograms to enhance clinical utility. Second, the follow-up duration of 2 years was relatively short. However, BCR after PCa surgery can occur 5 years or even later postoperatively. Short-term follow-up may underestimate the long-term recurrence risk of low-risk patients and fail to evaluate the predictive value of the combined detection for long-term survival. In subsequent studies, the follow-up duration should be extended to more than 5 years to analyze the utility of NLR and suPAR in long-term prognosis, providing evidence for their long-term clinical application. Third, this study focused only on the static preoperative levels of NLR and suPAR, without exploring their dynamic changes after surgery. The changes in these indicators at different postoperative time points, such as 1 month, 3 months, 6 months postoperatively, may better reflect residual tumor status and treatment response than can a single preoperative test, and their predictive efficacy may be superior. Future studies can conduct dynamic monitoring to analyze the association between postoperative indicator changes and BCR, providing more accurate “dynamic evidence”.

Conclusions

This study is the first to confirm that preoperative NLR combined with suPAR has high predictive value for BCR after radical prostatectomy for PCa. The AUC of their combined detection is as high as 0.943, and it enables accurate risk stratification of patients with PCa. Mechanistically, the association of the 2 markers suggests a potential synergistic interaction between the inflammatory immunity and tumor invasion pathways in driving BCR. This hypothesis not only provides a new perspective for investigating the biological mechanism of PCa recurrence but also offers a practical tool for clinical management. Despite certain limitations, the results of this study open up a new direction for postoperative prognosis evaluation of PCa. In the future, with the improvement of multi-center prospective studies, long-term follow-up, and dynamic monitoring, NLR combined with suPAR is expected to become a routinely used prognostic biomarker panel in PCa clinical practice, laying a foundation for the realization of individualized diagnosis and treatment of PCa.

Data Availability Statement

All data generated or analyzed during this study are available upon request.